This invention relates to a signal recording apparatus and a signal recording method for recording a signal onto an optical recording medium and a signal playback apparatus and a signal playback method for playing back a signal from an optical recording medium.
As one of signal recording apparatus and signal playback apparatus which use, for example, an optical disk as an optical recording medium, an apparatus has been proposed which makes use of near field light produced by an optical element such as an SIL (Solid Immersion Lens) formed from a two-group lens or an SIM (Solid Immersion Mirror) including a single lens. An apparatus of the type described is disclosed, for example, in U.S. patent application Ser. No. 09/385,956 assigned to the assignee of the present patent application.
Utilization of such near field light as mentioned above makes it possible to further reduce the spot diameter in accordance with the need for higher density recording of an optical disk.
For example, an SIL is a lens of a high refractive index interposed between a condensing lens and an optical disk and having a shape of a spherical lens partly cut away. The SIL lens is disposed such that the spherical surface thereof is directed to the condensing lens side while the other surface thereof is directed to a signal recording surface of the optical disk. A two-group lens is formed from a combination of the SIL and the condensing lens.
Where such an SIL as described above is interposed between the condensing lens and the optical disk, a numerical aperture greater than a numerical aperture of the condensing lens can be realized. Consequently, the spot diameter can be further reduced in size as described above.
In order to use such an SIL as described above to record or play back a signal onto or from an optical disk, it is necessary, for example, upon recording, to condense a recording laser beam upon the SIL while the SIL is moved toward the optical disk such that the distance between an end face thereof (the surface opposing to the optical disk) and the signal recording surface of the optical disk is sufficiently small to allow near field light to be produced (smaller than xc2xd the wavelength of the light, typically less than 200 nm) and then perform gap control to make the distance fixed to make the size of the condensed light spot on the optical disk fixed.
Incidentally, when such near field light is used for recording or playback of an optical disk, two procedures are conventionally available including a procedure wherein a gap controlling process for placing the optical head and the optical disk into a near field state before rotation of the optical disk is started after the optical disk is clamped by the apparatus (hereinafter referred to as first related art procedure) and another procedure wherein gap control is performed after rotation of the optical disk is started (hereinafter referred to as second related art procedure).
With the first related art procedure, however, there is the possibility that dust floating in the air may stick to the surface of the optical disk before/after the optical disk is clamped.
Accordingly, in the later process for establishing a near field state, that is, in the process of performing gap control between the optical head and the optical disk and then starting rotation of the optical disk, dust is sometimes caught between the optical head and the optical disk, resulting in failure of the gap control, and this sometimes disables later appropriate recording or playback.
In the worst case, the dust caught between the optical head and the optical disk may render the gap controlling operation unstable to such a degree that the optical head collides with and breaks the optical disk.
In order to prevent such sticking of dust as described above, it is a possible solution to cover the recording and/or playback apparatus with a clean booth to suppress dust which floats in the air around the recording and/or playback apparatus.
This solution, however, gives rise to another problem that an increased cost of equipment is required because the clean booth must be prepared.
Meanwhile, with the second related art procedure described above, if dust is present on the optical disk, then when the optical head is moved toward the disk in order to perform the gap control, the dust is caught between the optical head and the optical disk, rendering the gap control unstable.
In this instance, since the optical disk is rotating, there is the possibility that the optical disk may be damaged over an overall circumference. Further, if the optical head collides with the disk as a rotating body, then increased damage may be given to both of the optical head and the disk when compared with that when the disk stands still.
It is an object of the present invention to provide a signal recording apparatus, a signal playback apparatus and controlling methods for them wherein, when near field light is used for recording or playback of an optical disk, dust on the optical disk can be removed effectively and signal recording or signal playback based on stable gap control can be performed with a less expensive configuration.
It is another object of the present invention to provide a signal recording apparatus, a signal playback apparatus and controlling methods for them wherein, when near field light is used for recording or playback, a disk is rotated after gap control is performed thereby to allow recording or playback with near field light to be performed stably.
In order to attain the objects described above, according to an aspect of the present invention, there is provided a signal recording apparatus, including driving means for carrying and driving an optical recording medium to rotate, optical means disposed in the proximity of the optical recording medium for condensing near field light originating from a laser beam upon the optical recording medium, signal recording means for moving the optical means to a position in the proximity of the optical recording medium and using the near field light to record a signal onto the optical recording medium, and control means for controlling the driving means to rotate the optical recording medium before the optical means is moved to the position in the proximity of the optical recording medium by the signal recording means.
In the signal recording apparatus, the optical recording medium is rotated by the driving means under the operation control of the control means before the optical means is moved to the position in the proximity of the optical recording medium by the signal recording means.
Consequently, even if dust sticks to the optical recording medium or dust floats around the optical recording medium, such dust on the optical recording medium can be removed effectively by the rotation of the optical recording means before gap control for allowing recording of the optical recording medium to be performed subsequently using near field light is performed. Consequently, signal recording by stabilized gap control can be performed with a less expensive configuration.
According to another aspect of the present invention, there is provided a signal playback apparatus, including driving means for carrying and driving an optical recording medium to rotate, optical means disposed in the proximity of the optical recording medium for condensing near field light originating from a laser beam upon the optical recording medium, signal playback means for moving the optical means to a position in the proximity of the optical recording medium and using the near field light to play back a signal from the optical recording medium, and control means for controlling the driving means to rotate the optical recording medium before the optical means is moved to the position in the proximity of the optical recording medium by the signal playback means.
Also in the signal playback apparatus, the optical recording medium is rotated similarly by the driving means under the operation control of the control means before the optical means is moved to the position in the proximity of the optical recording medium by the signal recording means.
Consequently, even if dust sticks to the optical recording medium or dust floats around the optical recording medium, such dust on the optical recording medium can be removed effectively by the rotation of the optical recording means before gap control for allowing playback of the optical recording medium to be performed subsequently using near field light is performed. Consequently, signal playback by stabilized gap control can be performed with a less expensive configuration.
According to a further aspect of the present invention, there is provided a controlling method for a signal recording apparatus, including the steps of carrying and driving an optical recording medium to rotate thereby to remove dust on the optical recording medium, moving optical means disposed in the proximity of the optical recording medium to a position in the proximity of the optical recording medium so that near field light originating from a laser beam is condensed upon the optical recording medium, and recording a signal onto the optical recording medium using the near field light.
In the controlling method for a signal recording apparatus, the optical recording medium is rotated before the optical means is moved to the position in the proximity of the optical recording medium.
Consequently, even if dust sticks to the optical recording medium or dust floats around the optical recording medium, such dust on the optical recording medium can be removed effectively by the rotation of the optical recording means before gap control for allowing recording of the optical recording medium to be performed subsequently using near field light is performed. Consequently, signal recording by stabilized gap control can be performed with a less expensive configuration.
According to a still further aspect of the present invention, there is provided a controlling method for a signal playback apparatus, including the steps of carrying and driving an optical recording medium to rotate thereby to remove dust on the optical recording medium, moving optical means disposed in the proximity of the optical recording medium to a position in the proximity of the optical recording medium so that near field light originating from a laser beam is condensed upon the optical recording medium, and recording a signal onto the optical recording medium using the near field light.
Also in the controlling method for a signal playback apparatus, the optical recording medium is rotated before the optical means is moved to the position in the proximity of the optical recording medium.
Consequently, even if dust sticks to the optical recording medium or dust floats around the optical recording medium, such dust on the optical recording medium can be removed effectively by the rotation of the optical recording means before gap control for allowing playback of the optical recording medium to be performed subsequently using near field light is performed. Consequently, signal playback by stabilized gap control can be performed with a less expensive configuration.